Resonant mechanical structures are commonly employed as sensor elements for detecting the presence of biological or chemical analytes. Such detection is typically based on functionalizing the resonant mechanical structure such that the analyte or analytes of interest can bind to the mechanical resonator, if they are present. The binding of analytes to the mechanical resonator alters the resonant frequency of the mechanical resonator due to the mass of the bound analytes. Measurement of the resonant frequency of the mechanical resonator can thereby provide a sensitive indication as to the presence of the analytes.
In order for such sensors to provide high sensitivity, it is important for the mechanical resonator to have low mechanical loss, which is frequently expressed in terms of the resonator having a high quality factor (i.e., high Q). High Q results in a reduction of measurement noise, thereby improving sensitivity. However, it is challenging to provide high-Q mechanical resonators for use in liquid immersion applications, because liquid loading of the mechanical resonator due to immersion tends to significantly and undesirably decrease resonator Q.
In U.S. Pat. No. 6,906,450, resonator Q in immersion is electronically enhanced by providing electronic feedback control of the mechanical resonator. However, imposing a requirement on the sensor control electronics to provide appropriate Q-enhancing feedback may conflict with other sensor design considerations. Accordingly, it would be an advance in the art to provide mechanically resonant sensors having intrinsically high Q in fluid immersion.